WO2017016705A1

WO2017016705A1 - Method for decelerating a vehicle

Info

Publication number: WO2017016705A1
Application number: PCT/EP2016/062127
Authority: WO
Inventors: Edith Mannherz; Tobias Putzer
Original assignee: Robert Bosch Gmbh
Priority date: 2015-07-27
Filing date: 2016-05-30
Publication date: 2017-02-02
Also published as: JP6752877B2; EP3328695B1; JP2018523606A; EP3328695A1; US10919530B2; DE102015214117A1; CN107848514A; US20180215384A1

Abstract

In a method for decelerating a vehicle, the braking system of which comprises a hydraulic vehicle brake and an electromechanical braking mechanism, the electromechanical braking mechanism is actuated and a decelerating moment is additionally generated in the powertrain in case of a failure of the hydraulic vehicle brake.

Description

description

title

The invention relates to a method for braking a vehicle, which is equipped with a brake system with a hydraulic vehicle brake and moreover with an electromechanical brake device with an electric brake motor. State of the art

DE 10 2006 048 910 A1 describes a parking assistance system for a vehicle which assists the driver during a parking operation. In such parking assistance systems, the surroundings of the vehicle are scanned with sensors and the vehicle is automatically braked when it approaches too close to another object, such as a parked vehicle. The braking process is carried out regularly on the operating brake system of the vehicle, which is usually a hydraulic

Vehicle brake acts.

According to DE 10 2006 048 910 AI, the function of the operating brake system is monitored during a parking operation and, in the event of a detected fault, instead of the operating brake system either an automatic

Parking brake applied or the vehicle braked via an automatic transmission. The automatic parking brake includes an electric motor via which a

Brake piston is subjected to force against a brake disc. When an intervention in the automatic transmission, the parking position is engaged to generate braking force.

Disclosure of the invention The method according to the invention relates to the deceleration of a vehicle which is equipped with a brake system, which on the one hand comprises a hydraulic vehicle brake and on the other hand an electromechanical brake device with an electric brake motor. The

Electromechanical brake device with brake motor is commonly used as a parking or parking brake to produce a fixed the vehicle at a standstill clamping force. Upon actuation of the electric brake motor, the rotational movement of the rotor of the brake motor is transferred into an axial adjusting movement of a spindle, via which a brake piston, which carrier of a brake lining, is pressed axially against a brake disk. The brake piston is preferably the brake piston of the hydraulic vehicle brake, which is acted upon by the hydraulic brake pressure against the brake disk.

The electromechanical brake device with the electric brake motor is preferably used only in the low speed range, which is typical for parking operations. In principle, however, is also used at higher speeds and / or regardless of parking operations in

Consideration.

In the method for braking the vehicle is in the event that the hydraulic vehicle brake partially or completely fails and the

Vehicle thus not or not completely on the hydraulic

Vehicle brake can be braked, the electric brake motor of the electromechanical brake device is actuated to generate a braking force. In addition, a decelerating torque is generated in the drive train of the vehicle, so that overall the vehicle is braked not only on the electromechanical braking device, but also on the decelerating torque in the drive train. The drive train in the vehicle comprises at least one drive motor and a transmission for transmitting the

Drive movement of the drive motor to the wheels of the vehicle. The procedure with the decelerating torque in the drive train has the advantage that overall a higher braking force is available and Accordingly, the vehicle can be braked in a shorter time and possibly brought to a standstill.

The electromechanical brake device usually has to first travel an idle path before the brake pad on the brake piston comes into contact with the brake disc and a braking force can be built up. During the idle travel is in the electromechanical braking device no

Braking power available. However, in this phase can already over the

Drivetrain a decelerating moment are generated, so that the

Period in which no deceleration takes place, significantly shortened,

if necessary, reduced to zero. Usually, at the

inventive method in case of failure of the hydraulic

Vehicle brake first generates a decelerating torque on the engagement in the drive train and then a braking force on the

produced electromechanical braking device. It may be expedient to maintain the decelerating torque of the drive train beyond the time at which a braking force is provided in the electromechanical brake device. However, embodiments are also possible in which the decelerating torque of the drive train ends as soon as a sufficiently high braking force is available via the electromechanical brake device.

The method is preferably carried out in parked mode of the vehicle and is part of a parking assistance system with which the vehicle can be partially and completely autonomously switched on and / or parked in parking mode. The parking operation is carried out in particular only below a limit speed. The parking assistance system includes a sensor in the vehicle, via which the distance to surrounding obstacles such as parked vehicles is measured, and a control or control device in which processes the sensor data and control signals for controlling the electromechanical braking device are generated.

It is also possible to perform the automatic deceleration method independently of park operation, but preferably below one Limit speed. Optionally, the method for deceleration is also performed independently of a limit speed.

According to a further advantageous embodiment, after the failure of the hydraulic vehicle brake initially in the electromechanical

Brake device initiated a Zuspann- or braking operation and only after this, the drive train adjusted so that a decelerating torque is generated. This ensures that the free travel in the electric brake motor can be overcome in the shortest possible time and a clamping force can be generated in the electromechanical brake device. But it is also possible to actuate the electromechanical

To perform braking device and the adjustment of the drive train simultaneously or first the drive train to produce a

decelerating torque and then the

to operate electromechanical braking device.

According to another expedient embodiment, which relates to a vehicle with automatic transmission, in the automatic transmission, which is part of the drive train, the smallest possible gear ratio is set. The

smallest possible gear is speed-dependent, wherein in a performance of the method in parking mode, the smallest possible gear is usually the first gear. At higher speeds can

if necessary, a higher gear can be set as the lowest possible gear. The smallest possible gear ratio ensures that a maximum possible engine drag torque acts as a decelerating torque.

As drive motor, which is part of the drive train, come both

Combustion engines as well as electric motors into consideration, which are used either as the sole drive source or, in the case of a hybrid drive, in combination. As far as an internal combustion engine is present in the drive train, this is switched off, according to a further expedient embodiment, for braking the vehicle. This ensures that the maximum possible engine drag torque for braking the vehicle can be exploited. In the case of one or more electric motors in the drive train, which are present either alone or in addition to an internal combustion engine, these are advantageously switched to the braking operation of the vehicle in the generator mode. As a result, a motor braking torque is generated in the electric motor, which brakes the vehicle; in addition, the vehicle battery is charged.

According to another expedient embodiment, at least one

Electric motor in the drive train accelerates against the direction of travel. The vehicle moves against the effective direction of the electric drive motor, whereby a decelerating torque is generated.

According to a further expedient embodiment, which relates to a vehicle with four-wheel drive, a center differential is locked to the front and rear axles, so that the front and rear axles are kinematically coupled and rotate together and acts on all wheels a braking torque. In four-wheel drive vehicles this can be transmitted an increased braking torque. The various method steps for braking the vehicle are performed in a control unit in the vehicle, in which

Control signals for controlling the adjustable components of both the

Brake system and the drive train are generated. Further advantages and expedient embodiments can be taken from the further claims, the description of the figures and the drawings. Show it:

1 is a schematic representation of a four-wheel drive vehicle, Fig. 2 shows a section through an electromechanical parking brake for a

Vehicle in which the clamping force is generated by an electric brake motor,

3 is a flowchart with method steps for braking the

Vehicle in park mode in case of failure of the hydraulic Vehicle brake, shown for a vehicle with front or

Rear-wheel drive,

Fig. 4 is another flowchart for braking a vehicle in

Parking operation, shown for a four-wheel drive vehicle,

Fig. 5 is another flowchart for braking a vehicle in

Park operation, shown for a vehicle with electric motor drive.

1 shows an all-wheel drive vehicle 20 with hydraulic vehicle brakes 21 on each vehicle wheel 22. The drive train of the vehicle 20 is formed by an internal combustion engine 23 and a downstream automatic transmission 24. The vehicle 20 may have a hybrid drive with an electric drive motor 25 flanged to the automatic transmission 24. The drive movement of the internal combustion engine 23 and possibly of the electric drive motor 25 is transmitted to the front axle 26 of the vehicle and via a center differential 28 to the rear axle 27.

The adjustable components of the vehicle 20, in particular the

hydraulic vehicle brake 21, the components of the drive train with internal combustion engine 23, automatic transmission 24 and optionally the electric drive motor 25 and the center differential 28 are adjusted via control signals of a control or control device 12.

The vehicle 20 is further provided with an electromechanical

Braking device equipped with an electric brake motor, which as Parkbzw. Parking brake for generating a vehicle at a standstill of the stuck clamping force is used. Such an electromechanical

Braking device 1 is shown in Fig. 2.

The electromechanical brake device 1 comprises a caliper 2 with a pair of pliers 9, which engages over a brake disk 10. As an actuator, the parking brake 1, a DC electric motor as a brake motor 3, the rotor shaft rotatably drives a spindle 4, on which a spindle nut 5 is rotatably mounted. Upon rotation of the spindle 4, the spindle nut 5 is axially adjusted. The spindle nut 5 moves within a brake piston 6, which is a carrier of a brake pad 7, which is pressed by the brake piston 6 against the brake disk 10. On the opposite side of the

Brake disk 10 is another brake pad 8, which is held stationary on the pliers 9.

Within the brake piston 6, the spindle nut 5 can at a

Rotary movement of the spindle 4 axially forward in the direction of the brake disc 10 or at an opposite rotational movement of the spindle 4 axially to the rear to reach a stop 1 1 move. To generate a clamping force, the spindle nut 5 acts on the inner end face of the

Brake piston 6, whereby the axially displaceably mounted in the electromechanical brake device 1 brake piston 6 is pressed with the brake pad 7 against the facing end face of the brake disc 10.

Also, the brake motor 3 is controlled by the control or control unit 12, which is installed in the vehicle. The control or control unit 12 supplies as output a supply voltage U _S o, with which the electric brake motor 3 is acted upon.

The parking brake and the hydraulic vehicle brake 21 both act on the brake piston 6. Upon actuation of hydraulic vehicle brake 21, the brake motor facing the rear side of the brake piston 6 is pressurized with pressurized hydraulic fluid.

FIG. 3 shows a flowchart for braking a vehicle in parking mode in the event that the hydraulic vehicle brake fails during a parking operation, which is possibly carried out at least partially automatically. The vehicle has as a drive to an internal combustion engine, to which an automatic transmission is coupled. In the vehicle, only either the rear axle or the front axle is driven.

First, in the first method step 30, the failure of the hydraulic vehicle brake is detected. In order nevertheless to be able to decelerate the vehicle accident-free, in the next method step 31, the electromechanical Braking device started over the electromechanical way a vehicle decelerating to a stop clamping force is generated.

In addition, a decelerating torque is generated via the drive train of the vehicle in order to shorten the braking process. This will be done in the next

Method step 32 checks whether the position of the automatic transmission is in the driving position. If this is not the case, the no-branching ("N") is continued following method step 33, in which the least gear ratio is engaged via control signals of a control or automatic control unit in the automatic transmission

continued.

If the query in step 32 shows that the position of the automatic transmission is in the driving position, the Ya branch C, Y "is immediately advanced, possibly after the lowest gear ratio has been engaged, to step 34, in which the drive motor embodied as an internal combustion engine in the vehicle In combination with the smallest gear in the world

Automatic transmission is set, a high engine drag torque is effective over which the vehicle is additionally braked.

In the following method step 35, the query is whether the vehicle is already. If this is not yet the case, the no-branch is returned again at the beginning of the query according to step 35 and the query is cycled again at cyclic intervals.

After the vehicle has stopped, the Ya branch is advanced to step 36, in which it is queried whether the desired target clamping force has been reached in the electromechanical brake device. This ensures that at different storage conditions,

possibly also when the vehicle is parked on a slope, a sufficiently high clamping force in the electromechanical braking device is effective, which permanently sets the vehicle. If the query in step 36 reveals that the target clamping force has not yet been reached, the no-branch is returned to the beginning of the query and the query is cycled again. In the meantime, will built an increasing clamping force in the electromechanical braking device.

If the query in step 36 indicates that the target clamping force has been reached, the Ya branch is advanced to step 37, completing the process. In the electromechanical brake device, a sufficiently high clamping force is effective and the vehicle is at a standstill.

The method sequence according to FIG. 3 relates to a vehicle with

internal combustion engine drive and a driven vehicle axle. In contrast, FIG. 4 shows a method sequence for an emergency stop in the automatic parking mode of a vehicle with internal combustion engine, automatic transmission and four-wheel drive in the event that the hydraulic vehicle brake fails. Same process steps as in Fig. 3 are provided with the same reference numerals.

Analogous to FIG. 3, the failure of the hydraulic vehicle brake is also detected in FIG. 4 in step 30, and the emergency stop is initiated in step 31, by firstly starting the electromechanical brake device.

In the following step 100 it is queried whether the center differential between the front axle and rear axle is open. If this is the case, following the YES branch, step 101 is advanced and the center differential is blocked, whereupon the next step 32 is advanced. If, on the other hand, the query in step 100 shows that the center differential is not open, the blocking position is already present and the next branch 32 is advanced directly following the no branch.

The next method steps 32 to 37 correspond to those of FIG. 3. In step 32, the gear position is queried, in step 33, if necessary, set the smallest gear in the transmission. In step 34, the internal combustion engine is turned off, in step 35, the query is made whether the vehicle is stationary. In step 36 it is queried whether the target clamping force in the electromechanical

Braking device has already been achieved. In step 37, the method terminated after the target clamping force has been set and the vehicle is at a standstill.

In Fig. 5 is a procedure for a deceleration of a vehicle in

Park operation in case of failure of the hydraulic vehicle brake for a

Vehicle shown with electric motor drive. Also in Fig. 5 are the same process steps as in Fig. 3 and 4 provided with the same reference numerals.

In step 30, the failure of the hydraulic vehicle brake is detected, whereupon in step 31 the emergency stop is initiated and the electromechanical brake device is started. In the following step 200, a query is made as to whether the vehicle is moving forwards or reversing. If the vehicle is moving, the branching is followed by branching to step 201 and the electric drive motor is accelerated in the opposite direction to the direction of movement of the vehicle. As a result, the vehicle decelerating torque is generated via the electric drive motor. Following step 201, the query is returned to step 200 and cyclically

Checked intervals again, whether the vehicle is still moving.

If the query in step 200 reveals that the vehicle is at rest, following the no-branching step advances to step 202 and adjusts the drive of the electric drive motor to prevent the vehicle from accelerating out of the vehicle in the opposite direction. However, if the vehicle is on a slope and on the electromechanical

Brake device is still no sufficient clamping force is available, the electric drive motor is driven in step 202 in such a way that a force compensating the downhill force is generated in the drive motor.

Steps 36 and 37 correspond to those of FIGS. 3 and 4. In step 36, it is queried whether in the electro-mechanical brake device

Target clamping force has been achieved. If this is the case, in step 37, the electric drive motor is turned off, the process is completed.

Claims

claims

1 . Method for braking a vehicle (20), the braking system of which is a hydraulic vehicle brake (21) and an electromechanical brake

Brake device comprising an electric brake motor (3), wherein in case of failure of the hydraulic vehicle brake (21) of the brake motor (3) of the electro-mechanical brake device for generating a braking force actuated and additionally in the drive train of the vehicle (20)

decelerating torque is generated.

2. The method according to claim 1, characterized in that the method is carried out only below a limit speed.

3. The method according to claim 1 or 2, characterized in that the

Procedure is carried out in parking mode.

4. The method according to any one of claims 1 to 3, characterized in that after the failure of the hydraulic vehicle brake (21) first actuates the electromechanical braking device and then the drive train is adjusted in such a way that a decelerating torque is generated.

5. The method according to any one of claims 1 to 4, characterized in that in an automatic transmission (24) in the vehicle (20) the smallest possible gear ratio is set.

6. The method according to any one of claims 1 to 5, characterized in that an internal combustion engine (23) is switched off in the drive train.

7. The method according to any one of claims 1 to 6, characterized in that an electric motor is switched in the drive train in the generator mode.

8. The method according to any one of claims 1 to 6, characterized in that an electric motor in the drive train is accelerated against the direction of travel.

9. The method according to any one of claims 1 to 8, characterized in that a center differential (28) between the front and rear axles (26, 27) of a four-wheel drive vehicle is locked.

10. regulating or control device (12) for carrying out the method according to one of claims 1 to 9.

1 1. Vehicle having a braking system, which comprises a hydraulic vehicle brake (21) and an electromechanical braking device with an electric brake motor (3), with a control or control device (12) according to claim 10 for controlling the adjustable components of

Brake system and the powertrain in the vehicle (20).